Machine for forming pistons of elliptical cross section



5 Sheets-Sheet 1 NvEzN-roh Stewart- CATIQQQELM.

Oct. 18, 1955 G. D. STEWART MACHINE FOR FORMING PISTONS OF' ELLIPTICALCROSS SECTION Filed Feb. 3, 1949 Guben.- D

Oct. 18, 1955 G, n. STEWART MACHINE FOR FORMING PISTONS OF ELLIPTICALCROSS SECTION 5 Sheets-Sheet 2 Filed Feb. 3, 1949 havana-rok Stewart M,/'mar auf Gilbert :D

clamav/- Oct. 18, 1955 G. D. STEWART MACHINE FOR FORMING PISTONS OFELLIPTICAL CROSS SECTION 5 Sheets-Sheet 3 Filed Feb. 3, 1949 NVE-NTO@(Silber-t D. Stewart" .A, MMM ,f a/ga dH-romvsyf Oct. 18, 1955 G. D.STEWART 2,720,805

MACHINE FOR FORMING PISTONS OF ELLIPTICAL CROSS SECTION Filed Feb. 5,1949 5 Sheets-Sheet 4 I' IEE? 69 NVELNTQY2`- Gilbert D. tewqr-U(Artemisa/f Oct. 18, 1955 G. D. STEWART MACHINE FOR F'ORMING PISTONS OF'ELLIPTICAL CROSS SECTION 5 Sheets-Sheet 5 Filed Feb. 3, 1949 kmr n fl.

n D. SQLLJOLY'A 'fw W155i# United States Patent O masse MACHENE FRFRMING PSTONS 0F ELLHTCAL CRSS SECTION Gilbert D. Stewart, Detroit,Mich., assigner to Ex-Ceil-O Corporation, Detroit, Mich., a corporationor' Michigan Application February 3, 1949, Serial No. 74,418

4 Claims. (Cl. 82-24?) The present invention pertains to machines forforming internal combustion engine pistons of special shape and, morespecifically, to a novel and improved machine of the general characterdisclosed in United States Patent No. 2,121,934 issued June 28, 1938, toIra l. Snader et al.

The pistons of modern internal combustion engines such as those used inaircraft must be designed for operation at high temperature, pressureand speed. Due to the unequal distribution of metal in the piston wallsresulting from the formation of wrist pin bosses, such pistons normallytend to expand unevenly. Thus, a piston which is perfectly round whensubjected to room temperature will tend to assume a distorted,out-of-round shape when subjected to the substantial operatingtemperature of the engine within which it may be used. To oset thistendency, engine designers have called for pistons having slightlydistorted initial shapes but which, when heated to operating temperaturewthin the engine, will then assume the optimum shape for bestperfomance. Designers have also found that a satisfactory way to achievethis result is to fasten each piston with a cross section approximatingthat of an ellipse having a minor axis slightly smaller than theV normaldiameter of the piston and with such axis lying generally parallel tothe axis of the wrist pin bosses.

Accordingly, the general aim of the invention is to provide a novel andimproved machine for turning pistons of the character set forth so as toimpart a predetermined elliptical shape thereto.

Another object is to provide a machine of the foregoing type adapted tofashion pistons of generally elliptical cross section and which willhave a predetermined longitudinal taper or are.

A further object is to provide a machine of the above character whichwill be susceptible of simple, rapid adjustment and high productionoperation.

Other objects and advantages will become apparent as the followingdetailed description proceeds, taken in connection with the accompanyingdrawings, wherein:

Figure l is a fragmentary front elevation of an illustrative machineembodying the invention, such machine being in condition to start anoperating cycle.

Fig. 2 is' a slightly exaggerated diagrammatical view illustrating thenature of the cut taken on a round work piece by the machine of Fig. l.

Fig. 3 is a view similar to Fig. l but with a portion of the supportingbridge broken away and the machine near the end of its operating cycle.

Fig. 4 is a slightly exaggerated diagrammatical View illustrating theaxial are on a piston produced by the action of the machine shown inFig. 1.

Fig. 5 is a fragmentary plan view of the machine in the conditionillustrated in Fig. l.

Fig. 6 is an enlarged fragmentary vertical sectional view takenlongitudinally through the tool holder and a portion of the spindleassembly.

Fig. 7 is a transverse sectional view through the tool holder taken inthe plane of the line 7-7 in Fig. 6.

Fig. 8 is an end elevation of the tool holder taken in the plane of theline 8 8 in Fig. 6.

Fig. 9 is a fragmentary vertical sectional view taken through themachine of Fig. 1 and detailing the spindle actuating yoke.

Fig. l0 is an enlarged fragmentary horizontal sectional view taken inthe plane of the line 10-10 of Fig. 9.

While the invention is susceptible of various modiications andalternative constructions, a preferred embodiment has been shown in thedrawings and will be described below in considerable detail. It shouldbe understood, however, that there is no intention to the invention tothe specic form disclosed, but on the contrary, the intention is tocover all modifications and alternative constructions falling within thespirit and scope of the invention as expressed in the appended claims.

Referring more specifically to the drawings, the invention is thereexempliiied in the form of an illustrative turning machine in which itfinds particular but by no means exclusive utility. The machine 20comprises a base 21 having appropriate Ways thereon to support and guidea work holding table 22, which in the present instance is longitudinallymovable therealong. Rigidly xed to the table 22 in any suitable manneris a work support 24 having adjacent its upper end an arm 25 extendinglongitudinally of the machine 20. The arm 25 has incorporated thereinsuitable detachable clamping means for securing thereto a hollowcylindrical work piece in the form of a rough machined piston P, thedetails of such clamping means being unimportant for present purposes.Mounted in overlyn'ng and straddling relation upon the base 21 is abridge or saddle 26. The latter, while movable relative tothe table 22and work support 24, may or may not be movable with respect to the base21. The bridge 26 serves as a support for a tool head 28 and an electricdriving motor 29 which transmits power to the tool head via belt 38 andpulleys 31, 32.

The tool head 28 of the machine 20 (Figs. l and 3) comprises astationary body 33 which rotatably supports therein a tubular spindle 34journalled in spaced apart bearings indicated diagrammatically at 35 and36, respectively. The pulley 32 is drivingly connected to the left handend of the spindle 34 (Fig. 10) as by means of a key 37 and a set screw38. The end of the spindle 34 remote from the pulley 32 is of somewhatlarger diameter than the opposite end portion andaterminates in anannular face plate 40. The latter has a tapered central socket 41extending into the diametrically enlarged portion of the spindle 34. Thesocket 41 is adapted to snugly receive a hollow tapered shank 42integral with a generally cup-shaped tool holder 43 which is drivinglymounted on the face plate 40. The opening of the tool holder 43 is ofsuitable size and depth to receive the work piece P as the latter ismachined. In the present instance,` the tool holder 43 carries a singlepoint cutting tool 44 mounted so as to project in a radial inwarddirection. The tool 44 may be adjustably secured in various radialpositions, within relatively narrow limits, by means of adjusting screw45 and locking plug 46.

Provision is made for moving the tool 44 in the proper v path to dene anelliptical cross section in the work piece P. This is accomplishedpreferably by mounting the tool head 28 with the longitudinal axis ofits spindle lying in a vertical plane passing through the longitudinalaxis of the work supporting arm 25 and work piece P, but skewed at aslight angle with regard to the latter axis. With the tool head thusmounted, the cutting tool 44 is caused Vto' move in an orbital path, theplane V(of which is inclined at a slight angle' to the axis of the arm25'and the work piece P. This orbital path, although above, the bridge26 has associated therewith a wedge broc/k 47 :-(.Fig.; having a ila-tupper surface 48 sloping downwardly in thedirection of the work holdingtable. 212.' Mountedat spaced' apart points along. the. surface 48 are apair of cleats or abutments 49 secured in place as by cap; screws 50.(The underside of the bodyv 33. is fashionedvv with( a planev surface VLVwhich` Vabut's the surfacev 48, the surface. SL-being interruptedv by apair of transverse groovesV 52.whieh house the cleats l49. To

permit. limited adjustment of the tool head 28. upon the wedge block 47,the grooves 52 are made substantially wider than thel cleats49; Setscrews. 53 carried. by'. the body 33 and adjustable from the exterior;thereof serve toclampit tothe'cleats 49.

Y Means is provided for automatically regulating the Ysize ofthe crosssection generated in the work piece P as the latter advances axiallyrelative to the cuttingrtool 44'.l This is accomplished in theV machine20 by the use of means for progressively changing=.the radial positionY' of the cutting tool 44A during its: period of engagement VWith thework piece P. Referring. more specifically to Figs. 3, 6,7 and 8, itwill be perceived'that a tool carry-V ing arnr- 54 is pivotallysecured'to the tool holder 43 as by means of a pin 55 located closetothe tool 44.

" The arm 54 runs generally parallela to the axis of the tool holder43,. terminating in a bifurcated endA portion comprising spaced apartknuckles 56. A biasing spring 518 tends to urgeV the bifurcated endofthe arm 54v toward anextreme radial outwardposition which correspondsto the extreme. radial inward position of the' cutting tool 44. Theradial position; of the Varm 54 and the tool Y44 is governed' bymeransof a slide 59 housedwithin a transverse bore 60 in the tool head andadapted to recipro-f cate within narrow limitsl along-the. bore 60.Adjacent oneend thereof, the slide 59Y is formed with. a pair ofdiametrically Vopposed notches 61Y which receive the.V knuckles 56 ofthe tool carrying arm 54. To counter` balance the weight of' the arm 54,a'portion of the tool Y holder wall diametrically opposite the arm 54 isthickened as'y at 62.

For the `purpose of coordinating the radial position of Y the tool 44andthe armv 54 with the relative bodily movement between.v the worksupport and the tool holder 43, a simple' yet highly Veffectivearrangement is utilized.

7 Briefly, such arrangement comprises displaceable. means carried by thebridge 26 and adapted,rwhen actuated'. by the approaching work support24, to rock the tool. carry- Y ingarm 54 Yand the tool 44 into thedesired radial position. In the present instance, the bridge-.26 carriesa linkage comprisinga control ybar 63, a rockable yoke 61,

andr aniactuating shaft 65 Vrotatable with the spindle 34VV butaxifa'llyslidable within'rthe, same. The bar 63 is. dis-- posed longitudinallyofthe machine 20, being. slidably supported. withina bore in the wedgeblock 47 by means of a pair of spacedV apart guide bushings 66. VThelatter serve: to maintain the bar. 63 inA alinement withk a bumper Y'67` on the worksupp'ort 24, the bumper being adapted to accost thefreeend of the-'bar 63 during the machining of the Work piece P. Y

The ro'ckable V yoke 64 (Figs. l, 3, 9 and I0) which Y translates theaxial movement of the control bar 63 into movement ofthe actuatingshafty 65, is provided with a pairrof bushings 68'; whichy Vengage acorresponding pairof fixed supporting trunnions 69, the latter beingmounted on the bridge or saddle 26 as by means of suitable brackets. Thedepending end of the yoke 64 terminates in a Vpair of spaced apartbosses 70, each having an inwardly projecting pivot pin 71 threadedlysecured thereto. `The pins 71 engage an enlarged abutment member 72rigidly fixed to the control barV 63. The member 72 is provided with apair of vertical slots 73 ofsuitable size to receive the inner ends4 ofthe pins 71 and to permit movement of the latter along the slots 73. Theupstanding Vend of the yoke 64 also terminates in a'pai'r of spacedapart bosses.

74, each of the latter carrying an inwardly projecting pivot pin 75.having a slide block 76 journalled thereon. The

blocks 76 are arranged for coaction with a Yrelatively large andsubstantially rectangular abutment member 78 mounted on the shaft 65adjacent the spindle driving pul- Vley 32. The member 78 is formedWithra relatively wide vertical groove 79fon-1either-side thereoftogslidably receive theblocks 76. l

lrrordet to eliminate excessivewear which. might `other-'Vv j Y wiseoccurin the parts'connecting the Vyoke 64. andthe.V rotating actuatingshaft 65, thev abutment member ,'18 is journalled on the shaft 65 as bymeans of a pair .of axially spaced bearings 80.. Theflatter arefmountedonda portionof the shaft 65 of reduced diameter and are locked. againstaxial movement. relative; thereto. by means of. a,l washer 81,A sleeve82,. washer 84, and retainer bossi 85. The, bearings.. 80 are4 protectedagainst the entry of chips` Y and other foreign material by means of endcaps 86 rigf Y idly attached to= the member 78.

For theY purpose of effecting reciprocatory movementof the slide 591mresponse. to axial movement of the actuating shaft 65, the end of thelatter adjacent the toolv holder Y '43l has a cam portion 88integraltherewith (Figs..6 and 8).

The cam portionf. 88 is slotted longitudinally over a sub-V stantialportion of itslength so as .to dene a pair of laterally spacedcamiingers 89 which straddle central portion 9020i the slide.. Each. ofthe fingers 89'is formed.

with a relatively flat. guide surface 91running substan tiall-yyparallel tof the'axis of the shaft 65 and. a; cam sur'- face` 92 havinga moderate curvature along itsf length..

'Freely journalled on centralI portion .90 of the slide 59' .andadapted. to shift the latter through coaction with each..

of the cam surfaces. 92V isv av Vpair of follower rollersg 94.

Freelyv journalled on pfin;95.v fixed tothe tool head 435 and`adaptedtobear against. the guide surfaces91 is. a pair of reactionrollers 96. The latter are disposed in strad- Y dling relation withzthe:central portion ofy the slide, such portion beingformed with an oblongslot 98. to effect clear'- ance with: the pin, 95 which doesV not movewith the slide..

With the arrangementtthus farrdescribed, the bumper 6710i the worksupport would engage the controlbar l63 only when moving to the left; asviewed=in Figs. 1 and 3l Thus, in order to1 position. the'. bar 63accurately' When-theV worksupport 24 is moving in the oppositedirection, some sort of. loading or biasing device must be utilized.IntheY f present. instance, suchdevice happens to bea fluid actuatorv99fmounted on thebridge 26 and. connected with the Y. end of thecontrol har 63 adjacent the yokeY 64. With this construction, when the`work support 24 moves tothe right (asviewed-in Figsj. l'and 3), theactuator99 causes the. Y Y' endV of the control bar 63 to remain in;engagement.

the bumper 67. Such actionV continuesV until adjustable stop j10`0 onthe bar 63r accosts guide bushing V66'of'tl'1e I Wedge block 47.

. To protect thejmachine 20 against Vabnormai'movement Y of certainparts and also to facilitate the setting up ofan automaticV operatingcycle, a plurality of limit switches and stops may be employed. Thusthere is fixed to the workY holding table 22 a dog bar 102v (WFig.l)rwhich5earriesV a. stop dog 104 and various other. control dogs. (notshown).

Rigidly securedto the base 21 in .position to. be actuated 'Y by the dog104 when the table 22 reaches its extreme. right hand Y'position (asviewedin Fig. l) is a klimit switch plunger 105.- The latter, when`actuated, serves to arrest thetable 22 against further rightwardmovement.

For the purpose of actuatingan appropriate control when the tool 44 hasreached either extreme of its radial movement, there is operativelyassociated with the yokeL 64 a pair of limit switches 106, 108. Theswitch 106 is arranged for actuation when the tool 44 has reached itsextreme radial inward position. .Under such circum-4 stances, themachine is in the condition indicated in Fig. 1 and the yoke 64 isinclined away from the work piece. To enable the yoke to trip the switch106, the former is provided with a leg 109 having an adjustable tip 110adapted to engage a roller 111 carried by a tripping arm 112 on theswitch 106. When the tool 44 reaches its extreme radial outwardposition, as indicated in Fig. 3, the yoke 64 inclines toward the workpiece and an extension 114 on the former accosts roller 115 and trippingarm 116 on the limit switch 108.

While the operation of the machine 20 will doubtless be readily apparentto those skilled in the art, a brief rsum thereof might be appropriateat this point. Assume first that the machine is in the condition of Fig.l with a work piece P secured skirt-Erst to the arm 25 and the cuttingtool 44 at its extreme radial inward position. Upon initiation of theoperating cycle, the tool head 28 is brought up to speed and the workholding table 22 slides toward the bridge 26. This brings the head endportion of the work piece into Contact with the tool 44 without causingengagement of the control bar 63 by the bumper 67. With further movementof the table 22 toward the bridge 26, the entire ring belt of the workpiece P is given an elliptical cross section which is substantiallyconstant axially of the work piece P. As the tool 44 commences tomachine the skirt portion of the work piece adjacent the ring belt, thebumper 67 accosts the end of the control bar 63 and causes the latter tomove leftward (as viewed in Figs. l and 3) toward its retractedposition. Such action produces a proportional movement of the yoke 64,the actuating shaft 65, the cam arms S9, the slide 59, the tool carryingarm 54, and nally, the cutting tool 44. With continued movement of thetabel 22 toward the bridge 26, the tool 44 is caused to moveprogressively outward and travels in an orbit of ever increasingdiameter. This causes the tool 44 to deiine in the work piece P asubstantially elliptical cross section of gradually increasing areatoward the skirted end of the work piece, thus producing the ared skirtindicated in Fig. 4. After the work piece P has been completelymachined, it is permitted to overrun the tool 44 by a slight amount. Byreason of the increasing steepness of the cam surfaces 92 as the extremeradial outward position of the tool 44 is approached, such action issuicient to move the tool clear of the periphery of the work piece andthus avoid an undesirable tool dragout line when the work piece iswithdrawn from the tool holder.

l claim as my invention:

l. In a machine for forming pistons of elliptical cross sectiongradually increasing in area axially thereof, the combination comprisinga base, a work support adapted to clamp a work piece with its axisextending along said base, a tool head, means for mounting said worksupport and said tool head for relative bodily movement along said base,a spindle journalled in said tool head for rotation about an axisintersecting the axis of the work piece and fixed with respect theretobut skewed with respect to the direction of said relative bodilymovement, a tool holder rotatable with said spindle, a cutting toolcarried by said tool holder and mounted for radial shifting movementtherein, cam and follower means for shifting said cutting tool radiallywithout changing the angle between the axes of said spindle and the workpiece, and a motion transmitting linkage interposed between said worksupport and said cutting tool, said linkage being disposed in positionto actuate said cam and follower means and thereby effect a progressivechange in the radial position of said cutting tool as an incident tosaid relative bodily movement between said work support and said toolhead.

2. In a machine for forming. axially flared pistons of elliptical crosssection from generally cylindrical Work pieces, the combinationcomprising a base, a bridge disposed in overlying and straddlingrelation with said base, a work holding table mounted on said base forlongitudinal sliding movement relative to said bridge, a work support onsaid table adapted to hold a work piece with its axis extending in thedirection of said relative longitudinal sliding movement, a supportingblock on said bridge, a tool head fixed to said supporting block andhaving an axis adapted to intersect the axis of the work piece at arelatively small acute angle, a hollow spindle journalled in said toolhead and terminating in a face plate, a generally cup-shaped tool holdermounted in abutment with said face plate and bodily rotatable therewith,a tool carrying arm rockably mounted in said tool holder, a slide insaid tool holder adapted to rock said tool carrying arm into variousradial positions, a control bar slidably mounted in said supportingblock and disposed for abutting engagement with said work support, anactuating shaft housed within said hollow spindle, cam means fixed tosaid actuating shaft for positioning said slide in response to axialmovement of said shaft, and a rockable yoke pivotally mounted on saidbridge and adapted to transmit axial motion from said control bar tosaid actuating shaft.

3. In a machine for forming axially ared pistons of elliptical crosssection from generally cylindrical Work pieces, the combinationcomprising a base, a hollow spindle and a Work holding table mounted onsaid base for longitudinal sliding movement relative to each other, saidspindle being rotatable about an axis skewed with regard to saidlongitudinal sliding movement, a work support fixed to said tableadapted to clamp a work piece with its axis extending in the directionof said relative longitudinal sliding movement and intersecting the axisof said spindle, a bumper on said work support, a tool holder mountedfor bodily rotation with said spindle, a tool carrying arm pivotallysecured to said tool holder for radial movement relative thereto, aslide in said tool holder adapted to rock said tool carrying arm intoVarious radial positions, a reciprocable control bar disposed forengagement with said bumper on said work support, loading means forurging said control bar toward said bumper, an actuating shaft housedwithin said hollow spindle and rotatable therewith but axially movabletherein, cam means xed to said actuating shaft for positioning saidslide in response to axial movement of said shaft, and a rockable yokeadapted to transmit axial motion from said control bar to said actuatingshaft.

4. In a machine for forming pistons of variable cross section, thecombination comprising a base, a work support mounted for longitudinalmovement on the base, a supporting block associated with the base, atool head on the supporting block, a cup-shaped tool holder mounted inthe tool head, said holder having a thickened wall portion runningaxially thereof, a tool carrying arm rockably mounted in said toolholder and located diametrically opposite said thickened wall portion, acutting tool xed to said arm, a reciprocable slide mounted in said toolholder and adapted to rock said arm radially, follower means on saidslide, cam means adapted to coact with said follower means to effectradial adjustment of said cam and said cutting tool, a control barmounted in the supporting block and disposed for abutting engagementwith the work support and connecting linkage between the control bar andthe reciprocable slide and the tool holder, whereby relative movementbetween the work support and the supporting block will effect a radialadjustment of the cutting tool.

(References on following page) References Cited inthe He of this patentUNITED VSTATES Pfsljlabrlgs I WhitneyY Feb.x 26, 1889 Se:ott. Sept. 26,1911 5` Banta Nov. 3, 191.4

Gosper 'Aug 2 1927 VStrindberg July 31., 1928 8 YVSnaid'cl' June 28,1938 'Gest Nov. 11, 1941 YLmr Dec. 2, 1947 Y Staat Sept. 1'2, 1950 -EatnApr. 15, 1952 FOREIGN PATENTS.

Germat1y. Sept. 27, V1938

